The physics of getting there
Getting into space is mostly a problem of speed. To stay in a low orbit around Earth, a vehicle must travel sideways at roughly 7.8 kilometers per second, or about 28,000 kilometers per hour. Rising above the atmosphere is the easy part. Reaching that orbital speed is hard and requires large amounts of fuel. Because a rocket carries its fuel with it, much of its initial mass is propellant, and the useful payload is a small fraction. That is why rockets are built in stages, discarding empty tanks along the way.
Early rocketry
Rockets themselves are old, with simple gunpowder rockets used in several parts of the world centuries ago. The modern idea of space travel developed in the late nineteenth and early twentieth centuries. Konstantin Tsiolkovsky, a Russian schoolteacher, worked out the basic mathematics of rocket propulsion and proposed staged rockets. Robert Goddard in the United States launched the first liquid-fueled rocket in 1926, and other pioneers worked in Germany and elsewhere.
During the Second World War, Germany developed the V-2, a long-range ballistic missile that reached the edge of space on suborbital trajectories. After the war, the United States and the Soviet Union both built on this technology, and its engineers and designs influenced early space programs.
The first satellites and the first humans in space
On October 4, 1957, the Soviet Union launched Sputnik 1, the first artificial satellite. It was a small sphere, but its impact was large. The United States launched its first satellite in early 1958. In the late 1950s, animals were sent into orbit to learn whether living things could survive spaceflight.
In April 1961, Soviet cosmonaut Yuri Gagarin became the first person in space and the first to orbit Earth. Weeks later, American Alan Shepard flew a short suborbital flight, and in 1962 John Glenn became the first American to orbit. Valentina Tereshkova became the first woman in space in 1963. The competition between the two countries during this time is often called the space race.
To the Moon
In 1961, the United States set the goal of landing a person on the Moon. Over the 1960s, programs of increasing complexity tested spacewalks, rendezvous and docking in orbit, and the long-duration flights that would be needed. In July 1969, Apollo 11 landed two astronauts on the Moon while a third remained in lunar orbit. Several more landings followed, with the last crewed lunar landing taking place in 1972. In total, twelve people have walked on the Moon, all during that period.
Space stations and reusable vehicles
After Apollo, the focus shifted to staying in orbit, and space stations became the main destination. The Soviet Union launched the first space station, Salyut 1, in 1971, and the United States operated Skylab in the 1970s. Later, the Russian Mir station hosted crews for years. The International Space Station, assembled in orbit from modules launched by several countries, began in 1998 and has been continuously occupied by rotating crews since 2000.
The Space Shuttle, a partially reusable system, flew from 1981 to 2011. It carried crews and cargo to orbit, deployed and serviced satellites, and helped build the station. Its operation also included two fatal accidents, in 1986 and 2003, which led to investigations and design changes. In the years since, many organizations have worked on reusable rockets to lower cost, and commercial spaceflight providers now offer launch services for both cargo and crew in several countries. China also developed its own crewed program and, in the 2000s, began sending its own astronauts into orbit.
Why human spaceflight is hard
Keeping people alive in space involves a long list of challenges.
- Life support. Crews need air, water, food, temperature control and waste handling. Systems recycle as much as possible, but resupply is still needed.
- Radiation. Beyond the protection of Earth’s magnetic field, exposure to cosmic rays and solar particles is a concern, and shielding is limited by mass.
- Microgravity. Long stays can cause bone and muscle loss, fluid shifts, and other changes. Crews exercise for hours each day to reduce these effects, and researchers continue to study astronaut health.
- Psychological factors. Confinement, isolation and distance from home can be stressful, and they become more important on longer missions.
- Safety and reliability. Launch and re-entry are among the riskiest phases, and the margin for error is small. Escape systems and extensive testing help, but cannot eliminate risk.
- Training. Preparing for spaceflight is a long process, as astronaut training covers technical skills, teamwork and emergency procedures.
Looking ahead without hype
Plans change often, and it is wise to be cautious with predictions about crewed missions to the Moon, Mars or elsewhere. Long-duration trips raise unsolved problems around radiation, life support and cost. Details of timelines are best checked with official sources close to the time.
This article has covered how people and vehicles reached space. The broader history of observing and studying the cosmos with telescopes and probes is a different story, and the two have developed side by side.